In MariaDB, an extra column TIME_MS has been added to the INFORMATION_SCHEMA.PROCESSLIST table. This column shows the same information as the column 'TIME', but in units of milliseconds with microsecond precision (the unit and precision of the TIME column is one second).

For details about microseconds support in MariaDB, see microseconds in MariaDB.

The value displayed in the TIME and TIME_MS columns is the period of time that the given thread has been in its current state. Thus it can be used to check for example how long a thread has been executing the current query, or for how long it has been idle.

select id, time, time_ms, command, state from
   information_schema.processlist, (select sleep(2)) t;
| id | time | time_ms  | command | state     |
| 37 |    2 | 2000.493 | Query   | executing |

Note that as a difference to MySQL, in MariaDB the TIME column (and also the TIME_MS column) are not affected by any setting of @TIMESTAMP. This means that it can be reliably used also for threads that change @TIMESTAMP (such as the replication SQL thread). See also MySQL Bug #22047.

As a consequence of this, the TIME column of SHOW FULL PROCESSLIST and INFORMATION_SCHEMA.PROCESSLIST can not be used to determine if a slave is lagging behind. For this, use instead the Seconds_Behind_Master column in the output of SHOW SLAVE STATUS.

The addition of the TIME_MS column is based on the microsec_process patch, developed by Percona.


Comments loading...
Content reproduced on this site is the property of its respective owners, and this content is not reviewed in advance by MariaDB. The views, information and opinions expressed by this content do not necessarily represent those of MariaDB or any other party.